The means he used to make his ass leave off kicking

From Tristram Shandy. I will for tomorrow find the quote referenced, which Sterne likely took from Burton’s Anatomy of Melancholy and Burton in his turn from Saint Jerome’s Life of Hilarion

If any thing in this world, which my father said, could have provoked my uncle Toby, during the time he was in love, it was the perverse use my father was always making of an expression of Hilarion the hermit; who, in speaking of his abstinence, his watchings, flagellations, and other instrumental parts of his religion—would say—tho’ with more facetiousness than became an hermit—’That they were the means he used, to make his ass (meaning his body) leave off kicking.’

It pleased my father well; it was not only a laconick way of expressing—but of libelling, at the same time, the desires and appetites of the lower part of us; so that for many years of my father’s life, ’twas his constant mode of expression—he never used the word passions once—but ass always instead of them—So that he might be said truly, to have been upon the bones, or the back of his own ass, or else of some other man’s, during all that time.